Loudmouth plugin: got rid of a few FIXME comments
Loudmouth: added an helper which simplifies a small function and will make things easier elsewhere
Loudmouth: worked on how presence for groupchat should be handled

More comments than code I fear... but it lays the path for a
future implementation.
Loudmouth: worked on the dialect's LM::Handler implementation

I just got a single FIXME down and wrote more comments than code,
but it lays the path for future enhancements
Fixed a few places where copyright assignment or license where unclear (#721610)